JP2013066334A - Power control method, power controller and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve power control capable of suppressing the peak value of input current at a low cost, even if a capacitor input type rectifier circuit is used.SOLUTION: The power control method is used for supplying a secondary load with AC power from an AC power supply 35 while rectifying by a capacitor input type regulator 10, and for supplying a heater 38 with AC power from the AC power supply 35. The power control method is provided with a first mode for turning a heater input current Ii2 flowing into the heater 38 on in the entire period of each half cycle, and a second mode for turning the heater input current Ii2 off in a period when an input charging current Ii3 resulting from the charging current Ic of the capacitor is flowing in the regulator 10 and turning the heater input current Ii2 on in other period. The first mode or the second mode is used selectively in the control.

Description

  The present invention relates to a power control method, a power control apparatus, and an image forming apparatus. The present invention is used for power control of an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine of these.

  An electrophotographic image forming apparatus normally operates when AC power is supplied from a commercial power source. An image forming apparatus generally has a DC load and an AC load, converts a part of the supplied AC power into DC power and supplies the DC load to the AC load without rectifying the AC power. Supply.

  FIG. 11 is a diagram illustrating types of power supplied to each unit of a general image forming apparatus 101. As shown in FIG. 11, a part of the AC power supplied from the AC power source 135 to the power control device 130 is converted to DC power, and the imaging unit GU, the intermediate transfer unit 140, the fixing unit 150, the control unit 134, And supplied to the operation unit 139. Examples of the DC load include a motor for driving each roller and each fan, an electronic component or an electronic circuit in the control unit 134, and the operation unit 139.

  Further, a part of the AC power supplied from the AC power source 135 is supplied to the fixing unit 150 without being rectified. Examples of the AC load include a heater that is a heat source for performing a fixing process in the fixing unit 150. In recent years, high-power heaters are used to realize short warm-up and high-speed printing.

  Common power control methods for AC loads include phase control and wave number control. Phase control is a control method in which AC power is supplied to a load from an arbitrary phase angle within a half cycle to a zero cross point, and the supplied power is varied by changing the phase angle.

  The wave number control is a control method in which the power supplied to the load is varied by turning on or off every half cycle with a half cycle of AC power as one unit.

  A control method that further improves these control methods has also been proposed. Such a control method is disclosed in Patent Document 1 and Patent Document 2, for example.

  The power control device 130 includes a regulator that converts AC power into DC power. The regulator includes a rectifier circuit for rectifying AC power. Generally, a capacitor input type rectifier circuit is used as the rectifier circuit.

  FIG. 12 is a diagram showing a configuration of a conventional power control apparatus 130. As shown in FIG. 12, the power control device 130 converts the AC power from the AC power source 135 into DC power and supplies it to the secondary load 137, and controls the AC power to the heater 138. A heater control switching unit 131 is provided.

  The regulator 110 includes a capacitor input type rectifier circuit 118, a switching circuit 117, a transformer 113, a diode 114, a second smoothing capacitor 115, and a secondary output circuit 116.

  The rectifier circuit 118 includes a bridge diode 111 constituted by four diodes, and a first smoothing capacitor 112. The rectifier circuit 118 rectifies the AC power input from the AC power supply 135. The AC power is full-wave rectified by the bridge diode 111 and smoothed by the first smoothing capacitor 112.

  The smoothed output from the first smoothing capacitor 112 becomes a high-frequency AC waveform by the switching circuit 117 being repeatedly turned on and off. The switching circuit 117 can be configured using, for example, a bipolar transistor or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

  The high-frequency AC power is transformed by the transformer 113, rectified by the diode 114, and smoothed by the second smoothing capacitor 115, thereby being converted to DC power. The secondary output circuit 116 performs feedback control on the switching circuit 117 so that a desired voltage can be generated. DC power generated by the power control device 130 is supplied to the secondary load 137.

  The heater 138 is supplied with AC power from an AC power source 135 via the heater control switching unit 131. The heater control switching unit 131 adjusts the temperature of the heater 138 by controlling the amount of power supplied using the power control method described above.

JP 2010-186218 A JP 2010-286649 A

  According to the control method described above, DC power and AC power are supplied to the secondary side load 137 and the heater 138, respectively, in the image forming apparatus 101. However, there are the following problems.

  That is, when AC power is rectified in the rectifier circuit 118, a charging current flows through the first smoothing capacitor 112. A rectified input current Ii101 flows into the rectifier circuit 118, and the rectified input current Ii101 includes an input charging current corresponding to this charging current. The input charging current is characterized by a short time width and a high peak value. In the rectified input current Ii101, the current value during a period when the input charging current is not flowing is substantially zero.

  FIG. 13 is a diagram showing waveforms of the input voltage Vi101 and the rectified input current Ii101 of the capacitor input type rectifier circuit 118. As shown in FIG. 13, the input voltage Vi101 is a sine wave, whereas the waveform of the rectified input current Ii101 rises and falls steeply and thus has a sharp portion. The pointed shape is the waveform of the input charging current. In FIG. 13, the current value is zero except during the period in which the input charging current flows, and the rectified input current Ii101 has a short time width and a high peak value.

  Since the rectified input current Ii101 has a short time width, there is a problem that the power factor is low and the efficiency is low. Further, since the peak value of the rectified input current Ii101 tends to be large, the peak value of the total input current that is the sum of the heater input current Ii102 and the rectified input current Ii101 input to the heater 138 via the switching control unit 131 is large. There is a problem that it is easy to become.

  If the peak value of the total input current becomes too large, it may adversely affect electrical equipment. For example, an outlet or a plug used for connecting the power supply may be damaged. In order to prevent such damage, the peak value of the total input current may be suppressed as much as possible, for example, within the current regulation value (for example, 15 A).

  In order to cope with this, it is conceivable to reduce the total input current by lowering the power specification of the heater 138. Further, it is conceivable to suppress the total input current by performing weight control for temporarily stopping the power supply to the heater 138 so that the power is not supplied to the heater 138 and the secondary load 137 at the same time. .

  However, in these methods, the degree of freedom in designing the image forming apparatus 101 is lowered, and the performance of the image forming apparatus 101 may be deteriorated, and print productivity may be impaired.

  In addition, when an element that does not have a self-extinguishing capability such as a triac is used as the heater control switching unit 131, since free switching control within an AC half cycle is impossible, fine phase control is performed. Can not do.

  Further, when a choke input type rectifier circuit is used instead of the capacitor input type rectifier circuit, the cost is increased, and the apparatus is increased in weight and size.

  Further, the power factor can be improved by using a PFC (Power Factor Correction) power source, but in this case, there is a problem that the cost is increased.

  The present invention has been made in view of the above-described circumstances, and its object is to achieve low-cost power control capable of suppressing the peak value of the input current despite the use of a capacitor input type rectifier circuit. It is to be realized.

  A power control method according to the present invention rectifies AC power from an AC power supply by a rectifier switching circuit of a capacitor input type and supplies it to a DC load, and supplies AC power from the AC power supply to the AC load. A first mode in which an AC load input current flowing into the AC load is turned on during the entire period of each half cycle, and a capacitor in the rectifying switching circuit in each half cycle of the AC load input current. A second mode in which the AC load input current is turned off during a period in which the input charging current resulting from the charging current of the current flows and the AC load input current is turned on during the other periods is provided. Control is performed by selecting and using the second mode.

  The image forming apparatus according to the present invention is an image forming apparatus provided with an AC load that operates with AC power and a DC load that operates with DC power. Capacitor input type rectification switching circuit for supplying DC power to the load, and turning on or off the AC load input current flowing into the AC load when supplying AC power supplied from the AC power source to the AC load. Switch means for controlling, charging current period detecting means for detecting a charging current period, which is a period during which an input charging current due to a charging current of a capacitor flows in the rectifying switching circuit, and a control operation of the switching means Control means for determining and giving an instruction to the switch means, the control means to the AC load In the first mode in which the AC load input current is turned on in the entire period of each half cycle, or in the charging current period in each half cycle of the AC load input current, the AC load input current is turned off and the rest During the period, the second mode in which the AC load input current is turned on is selected, and the control operation of the switch means is determined.

  Despite the use of a capacitor input type rectifier circuit, power control capable of suppressing the peak value of the input current can be realized at low cost.

1 is a diagram illustrating an example of an internal configuration of an image forming apparatus according to an embodiment of the present invention. 3 is a block diagram of a portion related to power control of the image forming apparatus. FIG. 1 is a diagram illustrating a configuration of a power control device of an image forming apparatus. It is a figure which shows the example of the waveform of an input voltage and a rectification input current. 6 is a flowchart illustrating operation mode selection processing in the image forming apparatus. It is a flowchart which shows operation | movement of a 1st mode. It is a flowchart which shows operation | movement of a 2nd mode. It is a figure which shows the example of the current waveform of each part in 1st mode. It is a figure which shows the example of the current waveform of each part in 2nd mode. 5 is a flowchart showing switching of operation modes depending on the operation state of the image forming apparatus. FIG. 3 is a diagram illustrating types of power supplied to each unit of a general image forming apparatus. It is a figure which shows the structure of the power control apparatus of the conventional image forming apparatus. It is a figure which shows the waveform of the voltage or electric current of each part of a capacitor | condenser input type rectifier circuit.

  FIG. 1 is a diagram showing an example of the internal configuration of an image forming apparatus 1 according to an embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 1 is an electrophotographic full-color image forming apparatus incorporating a tandem type print engine. The image forming apparatus 1 is an apparatus generally called a multifunction peripheral or MFP (Multi Function Peripherals), and is an apparatus that integrates functions such as copying, network printing (PC printing), fax, and scanner.

  The image forming apparatus 1 includes an image forming unit 20 and a paper feeding unit 60. The paper feed unit 60 is a paper feed cassette 61 for storing each size of paper YS, and a roller group 62 to 66 that takes out the paper YS stored in the paper feed cassette 61 one by one and sends it to the transport path HR. Is provided. The paper YS sent from the paper feed cassette 61 to the transport path HR advances in the arrow M1 direction.

  The roller groups 62 to 66 are specifically a pickup roller 62, a paper feed roller 63, a separation roller 64, a transport roller pair 65, and a registration roller pair 66. The pickup roller 62 takes out the paper YS from the paper feed cassette 61. The paper feed roller 63 sends the taken paper YS to the transport path HR. The separation roller 64 is installed at a position facing the paper feed roller 63 across the paper YS. The separation roller 64 separates the sheets YS one by one so that the plurality of sheets YS that are overlapped are not sent to the transport path HR. The transport roller pair 65 feeds the paper YS sent one by one along the transport path HR. The registration roller pair 66 temporarily waits for the sheet YS and then supplies the sheet YS to the intermediate transfer unit 40 at a predetermined timing.

  The image forming unit 20 forms an image on a sheet by an electrophotographic method, and includes an imaging unit U, an intermediate transfer unit 40, and a fixing unit 50.

  The imaging unit U includes imaging units UY, UM, UC, and UK corresponding to four colors of Y (yellow), M (magenta), C (cyan), and K (black), respectively. The respective imaging units UY, UM, UC, UK are arranged along the intermediate transfer belt 41 in this order. Each imaging unit UY, UM, UC, UK exposes the photosensitive drum 21, the charging charger 22, the surface of the photosensitive drum 21 to form an electrostatic latent image, and the electrostatic latent image for each color. A developing unit 24 for developing a toner image by developing the toner, a transfer charger 25 for transferring (primary transfer) the toner image to the intermediate transfer belt 41, a cleaner 26 for cleaning the surface of the photosensitive drum 21, and Does not include a transfer roller. By the imaging unit U, the toner images (toner images) of the respective colors are sequentially transferred onto the intermediate transfer belt 41 running in the arrow M2 direction so that the transfer positions are aligned.

  The intermediate transfer unit 40 is provided with an intermediate transfer belt 41 to which a toner image is transferred, a plurality of rollers 42, 43, 44, and a secondary transfer roller 45. The intermediate transfer belt 41 is supported by rollers 42 to 44, and travels in the direction of the arrow M2 when these are rotationally driven. The secondary transfer roller 45 is installed so as to face the roller 44 with the intermediate transfer belt 41 interposed therebetween. The secondary transfer roller 45 can be brought into contact with and separated from the intermediate transfer belt 41, and the transfer nip is interposed between the secondary transfer roller 45 and the roller 44 by the secondary transfer roller 45 being pressed against the intermediate transfer belt 41. Part is formed.

  The sheet YS is conveyed in synchronism with the travel of the intermediate transfer belt 41 and contacts the intermediate transfer belt 41 on which the toner image is formed at the transfer nip portion. By applying a bias voltage to the secondary transfer roller 45, the toner image formed on the intermediate transfer belt 41 is transferred (secondary transfer) onto the paper YS. The sheet YS on which the toner image is transferred by the secondary transfer is conveyed to the fixing unit 50.

  The fixing unit 50 includes a heating roller 51 having a heat source therein, a pressure roller 52 that forms a nip portion with the heating roller 51, and a paper conveyance guide 53. The sheet YS on which the toner image is formed is conveyed to the fixing unit 50. The paper YS is guided by the paper transport guide 53 and transported on the transport path HR, and is heated at the nipple portion formed by the heating roller 51 and the pressure roller 52. The toner is melted by heating, and the toner image is fixed on the paper YS. The heat source installed inside the heating roller 51 is not shown. For example, a halogen heater is used as the heat source.

  The sheet YS on which the toner image is fixed is transported on the transport path HR and discharged onto the tray 70.

  Next, power control in the image forming apparatus 1 will be described. FIG. 2 is a block diagram for explaining portions related to power control of the image forming apparatus 1, and FIG. 3 shows a configuration of the power control apparatus 30 of the image forming apparatus 1.

  As shown in FIG. 2, the image forming apparatus 1 includes a power control device 30 and a control unit 34 in addition to the elements described with reference to FIG. 1. Note that the secondary load 37 is an element of the image forming apparatus 1 to which DC power is supplied. The secondary side load 37 is an example of “DC load”.

  The secondary load 37 is, for example, a motor for driving each roller or each fan in the imaging unit U, the intermediate transfer unit 40, the fixing unit 50, the paper feeding unit 60, and the like. Since DC power is also supplied to operate the electronic circuit (electronic component) of the control unit 34, these electronic circuits are also included in the secondary side load 37. Also, DC power is used in each process such as formation of an electrostatic latent image on the photosensitive drum 21, transfer of the toner image to the intermediate transfer belt 41, and transfer of the toner image to the paper YS. Therefore, the load due to each of these processes may be included in the secondary load 37.

  Inside the heating roller 51, a heater 38 such as a halogen heater, which is a heat source, is installed as described above. AC power is supplied to the heater 38. In addition, a temperature sensor 39 that detects the temperature of the heater 38 and sends the detected temperature of the heater 38 to the control unit 34 as a temperature detection signal St is installed in the heating roller 51. For example, a thermocouple or a semiconductor sensor is used as the temperature sensor 39. The heater 38 is an example of “AC load”.

  The control unit 34 performs feedback control on the heater 38 based on the temperature detection signal St so that the heating roller 51 has a predetermined temperature.

  The AC power supply 35 supplies commercial AC power to the image forming apparatus 1. A part of the AC power supplied to the image forming apparatus 1 is supplied to the heater 38 via the power control device 30. A part of the power is converted into DC power by the power control device 30 and supplied to the secondary load 37 and the control unit 34.

  The power control device 30 includes a regulator 10, a rectified input current detection circuit 33, a zero cross detection circuit 32, and a heater control switching unit 31.

  As shown in FIG. 3, the regulator 10 includes a capacitor input type rectifier circuit 18, a transformer 13, a diode 14, a second smoothing capacitor 15, a secondary output circuit 16, and a switching circuit 17.

  The rectifier circuit 18 includes a bridge diode 11 and a first smoothing capacitor 12 configured by four diodes. The rectifier circuit 18 rectifies the AC power input from the AC power supply 35. The AC power is full-wave rectified by the bridge diode 11 and smoothed by the first smoothing capacitor 12. A charging current Ic flows through the first smoothing capacitor 12.

  The rectifier circuit 18 is a capacitor input type rectifier circuit, and has a configuration in which the first smoothing capacitor 12 is directly connected without a coil or the like being connected immediately after the output of the bridge diode 11.

  The output from the rectifier circuit 18 is adjusted to a predetermined constant voltage by a circuit connected to the subsequent stage of the rectifier circuit 18. A transformer 13 is connected to the subsequent stage of the rectifier circuit 18 via the switching circuit 17. The switching circuit 17 is repeatedly turned on / off at a predetermined interval by the control signal Sd from the secondary side output circuit 16, so that the DC output (pulsating current output) of the rectifier circuit 18 becomes a high-frequency AC waveform. The switching circuit 17 can be configured using, for example, a bipolar transistor or a MOSFET.

  The high-frequency AC waveform is transformed by the transformer 13, rectified by the diode 14, and smoothed by the second smoothing capacitor 15, thereby being converted into DC power. The secondary output circuit 16 performs phase control of the switching circuit 17 and feedback control so that a predetermined voltage is generated by the regulator 10. DC power generated by the power control device 30 is supplied to the secondary load 37.

  The rectification input current detection circuit 33 detects the magnitude of the rectification input current Ii1, which is the input current of the regulator 10, that is, the input current of the rectification circuit 18, and sends the detected value to the control unit 34 as the rectification input current detection signal Sii1. The component of the rectified input current Ii1 is a main component of the charging current Ic to the first smoothing capacitor 12, and a leakage current, a noise current, and other current components are added thereto. The rectified input current detection circuit 33 is configured using, for example, a current detection resistor.

  The zero cross detection circuit 32 detects the zero cross point of the AC voltage of the AC power supply 35 and sends the detected zero cross point to the control unit 34 as the zero cross detection signal Sz.

  The heater control switching unit 31 is turned on or off in response to the heater control signal Sh sent from the control unit 34. Thereby, the heater control switching unit 31 performs phase control of the AC power supplied to the heater 38. The heater input current Ii2 whose phase is controlled flows into the heater.

  The total input current Iia that appears later is the sum of the heater input current (AC load input current) Ii2 that flows into the heater 38 and the rectified input current Ii1 that flows into the rectifier circuit 18.

  The heater control switching unit 31 is configured by an element having a self-extinguishing capability such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). Thereby, it can be turned on or off at an arbitrary phase timing, and a heater input current Ii2 having a waveform as described later can be generated.

  The control unit 34 is configured using, for example, a CPU, a ROM, a RAM, an interface circuit, other peripheral circuits, a hardware circuit, or the like, and controls the operation of each unit of the image forming apparatus 1. Each unit of the image forming apparatus 1 operates in response to a command from the control unit 34, and the control unit 34 grasps and manages the operation state of each unit from a signal from each unit.

  The control unit 34 detects the peak value based on the rectified input current detection signal Sii1. As described above, the main component of the rectified input current Ii1 is the charging current Ic to the first smoothing capacitor 12, which has a relatively short predetermined time width Tc and a large peak value Pc in each half cycle of AC. . The peak value Pc and the time width Tc, particularly the peak value Pc, vary according to the size of the secondary side load 37.

  The control unit 34 stores a threshold value Ith for the rectified input current Ii1 in advance. The threshold value Ith is used to control the peak value (Pa) of the total input current Iia so that it does not become too large. That is, the peak value of the total input current Iia is used so that the use of the image forming apparatus 1 does not adversely affect an electrical device such as an outlet or a plug used for connection to the AC power supply 35 or damage the electrical device. (Pa) is suppressed.

  For example, if the peak value (Pa) of the total input current Iia is expected to exceed the current regulation value (Ik) of these electric devices, the phase control of the heater input current Ii2 is performed so as not to exceed. The threshold value Ith is used as a threshold value for detecting that the magnitude of the rectified input current Ii1, for example, the peak value (Pa) has reached its limit.

  This will be described in more detail below.

  That is, the control unit 34 controls the operation of the heater control switching unit 31 so that the peak value Pa of the total input current Iia is, for example, a value smaller than the current regulation value Ik of the electrical device.

  When the image forming apparatus 1 is in operation (in operation), the peak value of the heater input current Ii2 does not change much because the heater 38 needs a predetermined temperature even if the operation state changes. On the other hand, the peak value Pc of the rectified input current Ii1 varies greatly according to the operating state of the image forming apparatus 1. Therefore, by controlling the phase of the heater input current Ii2 according to the magnitude of the rectified input current Ii1, the peak value Pa of the total input current Iia is suppressed. For example, the peak value Pa does not exceed the current regulation value Ik. Can be controlled.

  In order to perform such control, the control unit 34 performs phase control of the heater control switching unit 31 in accordance with a change in the rectified input current Ii1 based on the rectified input current detection signal Sii1. By the phase control of the heater control switching unit 31, the ON period of the heater input current Ii2 flowing into the heater 38 is controlled.

  Specifically, for example, when the peak value Pc of the rectified input current Ii1 exceeds the threshold value Ith, the heater input current Ii2 is turned off in a period (charging period) corresponding to the charging current Ic of the rectified input current Ii1. The heater input current Ii2 is turned on only during a period other than the charging period.

  Here, the rectified input current Ii1 will be described.

  FIG. 4 shows an example of waveforms of the input voltage Vi1 and the rectified input current Ii1. In FIG. 4, of the waveform of the rectified input current Ii1, a portion represented by a solid line is a waveform of an input charging current Ii3 described later, and a portion represented by a broken line is a waveform other than the input charging current Ii3.

  In FIG. 4, the input voltage Vi1 is a sine wave, and only one cycle (time 0 to t6) is shown. At the input voltage Vi1, times 0, t3, and t6 are zero cross points.

  The rectified input current Ii1 is zero at time 0 to t1, rises at time t1, falls after reaching a peak, and becomes zero at time t2. It is zero at time t2 to t4, rises to the negative side at time t4, falls after reaching the peak, and becomes zero at time t5.

  In the rectifier circuit 18, the electric power rectified by the bridge diode 11 is charged in the first smoothing capacitor 12. When the voltage charged in the first smoothing capacitor 12 is larger than the voltage supplied from the bridge diode 11, the first smoothing capacitor 12 is discharged. When the voltage charged in the first smoothing capacitor 12 is smaller than the voltage supplied from the bridge diode 11, the first smoothing capacitor 12 is charged by the output of the bridge diode 11 without discharging.

  From time 0 to t1, t2 to t4, and t5 to t6, a current flows through the circuit on the load side due to the electric charge charged in the first smoothing capacitor 12. At this time, since charging to the first smoothing capacitor 12 is not performed, the charging current Ic does not flow.

  On the other hand, from time t1 to t2 and t4 to t5, the first smoothing capacitor 12 is charged by the output of the bridge diode 11, and the charging current Ic flows.

  Of the rectified input current Ii1 that flows into the rectifier circuit 18, an input charging current Ii3 that is a current that flows during the period of time t1 to t2 and time t4 to t5 is a current component that flows due to the charging current Ic.

  During each half cycle of the input voltage Vi1, an input charging current Ii3 of one pulse (one time) flows.

  Now, in order to perform the phase control of the heater control switching unit 31 described above, an operation mode (control mode) for that purpose is set in the control unit 34.

  Next, the operation mode by the control part 34 is demonstrated.

  The operation mode includes a first mode (first control mode) and a second mode (second control mode).

  In the first mode, the heater input current Ii2 flowing into the heater 38, which is an AC load, is turned on during the entire period of each half cycle. That is, phase control is not performed in the first mode.

  In the second mode, in each half cycle of the heater input current Ii2, the heater input current Ii2 is turned off during the period during which the input charging current Ii3 due to the charging current Ic flows (charging current period Tc), and during the other periods The heater input current Ii2 is turned on.

  In the present embodiment, the control unit 34 acquires the peak value Pc of the rectified input current Ii1 based on the rectified input current detection signal Sii1, and selects the first mode when the value is smaller than the threshold value Ith, Control in the first mode is performed. When the peak value of the rectified input current Ii1 is greater than or equal to the threshold value Ith, the second mode is selected, and control in the second mode is performed.

  Thus, for the phase control in the second mode, the zero cross detection signal Sz, that is, the zero cross points such as the times t1, t2, t4, and t5 are used. For the detection of the zero cross point, a threshold value Ithz close to zero can be used. In this case, the time when the rectified input current Ii1 (or input charging current Ii3, charging current Ic) crosses the threshold value Ithz is the zero cross point. In this case, the zero cross point may not be the timing when the rectified input current Ii1 becomes zero, or the timing when the input charging current Ii3 or the charging current Ic becomes exactly zero. As described above, it is possible to use a timing at which the rectified input current Ii1 or the like becomes almost zero or a timing at which a predetermined value near zero is used as the zero cross point.

  In the above description, the peak value Pc of the total input current Iia is compared with the threshold value Ith in order to select the operation mode. However, the operation mode may be determined in consideration of not only the peak value Pc but also the time width Tc.

  In the embodiment described above, the threshold value Ith has been described as being set so as to perform control so that the peak value Pa of the total input current Iia does not exceed the current regulation value Ik. However, in that case, instead of using the current regulation value Ik itself, an appropriate regulation value Ika corresponding to the current regulation value Ik may be used. That is, as the regulation value Ika, for example, a value obtained by multiplying the current regulation value Ik by an appropriate coefficient ka (Ik × ka), a value obtained by adding an appropriate constant kb to the current regulation value Ik (Ik + kb), or the like may be used. Good.

  Further, as the current regulation value Ik, the current regulation value of the electric device itself is not used, but the current regulation value taking into account the time width Tc of the input charging current Ii3, for example, the effective value of the rectified input current Ii1 or A current regulation value in consideration of an effective value of the total input current Iia or the like may be used.

  As described above, in the second mode, the total input current Iia is controlled so that the peak value Pa or other representative value does not become too large.

  Next, an example of the power control method of the image forming apparatus 1 will be described with reference to a flowchart and each current waveform.

  FIG. 5 is a flowchart showing operation mode selection processing in the image forming apparatus 1, FIG. 6 is a flowchart showing the operation in the first mode, and FIG. 7 is a flowchart showing the operation in the second mode. FIG. 8 is a diagram showing an example of the current waveform of each part in the first mode, and FIG. 9 is a diagram showing an example of the current waveform of each part in the second mode. FIG. 10 is a flowchart showing switching of operation modes depending on the operation state of the image forming apparatus 1.

  In FIG. 5, the rectified input current Ii1 is detected (# 501). The rectified input current Ii 1, that is, the peak value Pc included therein is always detected by the rectified input current detection circuit 33.

  The detected peak value Pc is compared with the threshold value Ith (# 502). When the peak value Pc is smaller than the threshold value Ith (No in # 502), the first mode is selected (# 503). When the peak value Pc is equal to or greater than the threshold value Ith (Yes in # 503), the second mode is selected (# 504).

  In FIG. 6, when the first mode is selected (# 601), based on the heater control signal Sh, the heater input current Ii2 is turned on in the entire period of each half cycle in the heater control switching unit 31. Control is performed (# 602).

  As shown in FIG. 8, in the first mode, the peak value Pc of the rectified input current Ii1 is smaller than the threshold value Ith. The heater input current Ii2 is in phase with the input voltage Vi1 and is on during the entire period of each half cycle. The total input current Iia has a waveform protruding near the center of each half cycle, but its peak value Pa is kept smaller than the current regulation value Ik. The total input current Iia is the sum of the rectified input current Ii1 and the heater input current Ii2.

  In FIG. 7, when the second mode is selected (# 701), the charging current period (time width) Tc is detected (# 702). Then, in each half cycle of the heater input current Ii2, the control is performed so that the heater input current Ii2 is turned on during the charging current period Tc and the heater input current Ii2 is turned on during the periods other than the charging current period Tc. (# 703).

  As shown in FIG. 9, in the second mode, the peak value Pc of the rectified input current Ii1 is larger than the threshold value Ith. The heater input current Ii2 has the same phase as that of the input voltage Vi1, but is OFF during a predetermined period tb1 to tb2, tb4 to tb5... Of each half cycle, that is, in each charging current period Tc. Thereby, the peak value Pa of the total input current Iia is suppressed to be smaller than the current regulation value Ik without protruding even in the vicinity of the central portion.

  In this way, the peak value Pa of the rectified input current Ii1 is detected, and the operation mode is selected according to the magnitude, so that the input current (total input) is used even though the capacitor input type rectifier circuit is used. The peak value Pa of the current Iia) can be suppressed.

  As a result, it is possible to perform control so as to conform to the current regulation value Ik of electrical equipment such as an outlet or a plug, and it is possible to prevent these electrical equipment from being adversely affected.

  In addition, since it is possible to avoid weight control for supplying power to the heater 38, the short-warm-up and high-speed printing of the image forming apparatus 1 are not hindered.

  In the embodiment described above, the operation mode is selected by detecting the peak value Pc and the like of the rectified input current Ii1. However, the operation mode may be selected or determined by other methods. That is, for example, a parameter indicating the size of the secondary load 37 may be detected in addition to the size of the peak value Pc of the rectified input current Ii1.

  For example, the first mode is selected when the size of the secondary load 37 is smaller than a predetermined value, and the second mode is selected when the size is larger than the predetermined value.

  Further, since the magnitude of the rectified input current Ii1 changes according to the operation state of the image forming apparatus 1, the operation state of the image forming apparatus 1 may be detected and the operation mode may be selected and determined according to the operation state. .

  Specifically, for example, the operation mode is determined depending on whether the image forming apparatus 1 is warming up, initial operation, standby, printing (printing), or the like. May be.

  That is, the rectified input current Ii1 is, for example, about 1 A when warming up or in standby, is, for example, about 3 A when initial operation is being performed, and is, for example, about 5 A when printing is in progress.

  Therefore, for example, the first mode is selected as the operation mode during warm-up or standby. In addition, when the initial operation or printing is in progress, the second mode is selected as the operation mode.

  Note that the standby state is a state where the image forming apparatus 1 is turned on but is not operating. That is, the control system such as the electronic circuit is operating in the secondary load 37, but the motor is hardly driven, and the rectified input current Ii1 is small. However, when the user intends to perform printing, the heating roller 51 is at a certain temperature because it must be ready for printing. Therefore, the heater input current Ii2 also flows.

  The term “warming up” refers to a state from when the image forming apparatus 1 is on standby until it is ready for printing. Since it is before printing is performed, the control system of the secondary load 37 is operating as in the standby mode, but the motor is hardly operating, and the rectified input current Ii1 is small. Although it depends on the temperature at that time, the heater input current Ii2 flows because the temperature of the heating roller 51 usually has to be increased.

  The initial operation is a state where printing is not performed but positioning of each part is necessary. Since the motor is driven to position each part, the rectified input current Ii1 is larger than during standby and warm-up. Since the temperature of the heating roller 51 has to be raised in order to enable printing, the heater input current Ii2 is also flowing.

  Also, “printing” means a state in which an image is formed on the paper YS, and a state in which the motors and the like of each part in the secondary load 37 are almost in operation. The heater 38 is also heated, and the heater input current Ii2 is also flowing.

  As described above, when the operation mode is selected according to the operation state of the image forming apparatus 1, it is not necessary to detect the rectified input current Ii1, and therefore the rectified input current detection circuit 33 can be omitted.

  In this case, the controller 34 may store in advance a preferable operation mode corresponding to the operation state of the image forming apparatus 1.

  Next, an example of selecting an operation mode according to the operation state of the image forming apparatus 1 will be described with reference to a flowchart.

  FIG. 10 is a flowchart illustrating an example of a processing operation for selecting an operation mode according to the operation state of the image forming apparatus 1.

  In FIG. 10, when the image forming apparatus 1 is warming up (WU) (# 1001), the first mode is selected (# 1002). Thereby, all necessary heaters such as the heater 38 are turned on in all cycles.

  When the initial operation is being performed (Yes in # 1003), the second mode is selected (# 1004). Thereby, the phase of the electric power supplied to the heater 38 and the like is controlled, and the peak value Pa of the total input current Iia is suppressed. If the initial operation is not in progress (No in # 1003), the first mode is selected (# 1005).

  When the warm-up is completed (# 1006) and the standby mode is set (# 1007), the first mode is selected (# 1008).

  When printing is started (# 1009), the second mode is selected (# 1010). When the printing is finished and the apparatus is shifted to the standby mode (# 1011), the first mode is selected (# 1012).

  As described above, in the image forming apparatus 1 according to the present embodiment, the sum of the AC load input current (heater input current Ii2) flowing into the AC load and the rectified input current Ii1 flowing into the regulator 10 is a predetermined current regulation value Ik. The ON / OFF timing in each half cycle of the AC load input current is controlled so as not to exceed.

  The image forming apparatus 1 according to the present embodiment includes the capacitor input rectification type rectifier circuit as described above, and can suppress the total input current Iia even though no PFC power source is used. Therefore, it can be easily realized at low cost that the peak value Pa of the total input current Iia does not exceed the current regulation value of the electrical equipment.

  Further, since the power specifications of the heater 38 are not limited, a high-power heater 38 can be used, and short warm-up and high-speed printing can be realized.

  Further, in the second mode, the waveform of the total input current Iia can be brought close to a sine waveform having the same phase as the input voltage Vi1, which contributes to improvement of the power factor.

  In addition, the structure which used the halogen heater as the heater 38 was illustrated. However, in addition to the halogen heater, a carbon heater, a heating wire, a ceramic heater, an induction heating (IH: Induction Heating) coil, or the like may be used.

  In the above-described embodiment, the configuration, structure, shape, and configuration of the regulator 10, the rectifier circuit 18, the power control device 30, the heater control switching unit 31, the rectification input current detection circuit 33, or the entire image forming apparatus 1 or each unit. The dimensions, circuits, number, material, processing contents or order or timing can be appropriately changed in accordance with the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Regulator 12 1st smoothing capacitor 18 Rectifier circuit 30 Power control apparatus 31 Switching part for heater control (switch means)
32 Zero cross detection circuit 33 Rectified input current detection circuit 34 Control unit (control means, charging current period detection means)
35 AC power supply 37 Secondary load (DC load)
38 Heater (AC load)
39 Temperature sensor 51 Heating roller Ii2 Heater input current (AC load input current)
Ii1 Rectified input current Ii3 Input charging current Iia Total input current Ith threshold Ic Charging current Tc Charging current period Pc Peak value

Claims (12)

A power control method for rectifying AC power from an AC power source by a capacitor input type rectification switching circuit and supplying the AC load to the DC load, and supplying AC power from the AC power source to the AC load,
A first mode in which the AC load input current flowing into the AC load is turned on for the entire period of each half cycle;
In each half cycle of the AC load input current, the AC load input current is turned off during the period in which the input charging current due to the capacitor charging current flows in the rectifying switching circuit, and the AC load input current during the other periods. A second mode in which is turned on, and control is performed by selecting and using the first mode or the second mode.
A power control method characterized by the above. Detecting a rectified input current flowing in the rectifying switching circuit;
When the rectified input current is smaller than a predetermined threshold, the first mode is selected,
Selecting the second mode when the rectified input current is greater than or equal to the threshold;
The power control method according to claim 1. A capacitor input type rectifier switching circuit that rectifies AC power from an AC power supply and outputs DC power, supplies the DC power to the DC load, and supplies AC power from the AC power supply to the AC load. A power control device,
Switch means for controlling on or off of an AC load input current flowing into the AC load when supplying AC power from the AC power source to the AC load;
Charging current period detection means for detecting a charging current period, which is a period during which an input charging current caused by a charging current of a capacitor flows in the rectifying switching circuit;
Control means for determining a control operation of the switch means and giving an instruction to the switch means,
The control means is a first mode in which the AC load input current flowing into the AC load is turned on in the entire period of each half cycle, or the charging current period in each half cycle of the AC load input current is the AC load. A second mode in which the input current is turned off and the AC load input current is turned on during other periods is selected, and the control operation of the switch means is determined.
The power control apparatus characterized by the above-mentioned. Rectification input current detection means for detecting a rectification input current flowing in the rectification switching circuit,
The control means selects the first mode when the detected rectified input current is smaller than a predetermined threshold value, and selects the first mode when the detected rectified input current is equal to or greater than the threshold value. Select two modes,
The power control apparatus according to claim 3. An image forming apparatus provided with an AC load operated by AC power and a DC load operated by DC power,
A capacitor input type rectification switching circuit for rectifying AC power supplied from an AC power source and supplying DC power to the DC load;
Switch means for controlling on or off of an AC load input current flowing into the AC load when supplying AC power supplied from the AC power source to the AC load;
Charging current period detection means for detecting a charging current period, which is a period during which an input charging current caused by a charging current of a capacitor flows in the rectifying switching circuit;
Control means for determining a control operation of the switch means and giving an instruction to the switch means,
The control means is a first mode in which the AC load input current flowing into the AC load is turned on in the entire period of each half cycle, or the charging current period in each half cycle of the AC load input current is the AC load. A second mode in which the input current is turned off and the AC load input current is turned on during other periods is selected, and the control operation of the switch means is determined.
An image forming apparatus. Rectification input current detection means for detecting a rectification input current flowing in the rectification switching circuit,
The control means selects the first mode when the detected rectified input current is smaller than a predetermined threshold value, and selects the first mode when the detected rectified input current is equal to or greater than the threshold value. Select two modes,
The image forming apparatus according to claim 5. The control unit selects the first mode or the second mode based on an operating state of the image forming apparatus;
The image forming apparatus according to claim 5. The control unit selects the first mode when the image forming apparatus is warming up;
The image forming apparatus according to claim 7.   The image forming apparatus according to claim 7, wherein the control unit selects the second mode when the image forming apparatus is printing. The control unit selects the first mode when the image forming apparatus is on standby;
The image forming apparatus according to claim 7. The control unit selects the second mode when the image forming apparatus is in an initial operation;
The image forming apparatus according to claim 7. A power control method for rectifying AC power from an AC power source by a capacitor input type rectification switching circuit and supplying the AC load to the DC load, and supplying AC power from the AC power source to the AC load,
ON or OFF in each half cycle of the AC load input current so that the sum of the AC load input current flowing into the AC load and the rectified input current flowing into the rectifying switching circuit does not exceed a predetermined current regulation value. Control the timing,
A power control method characterized by the above.

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